It returns

 Filing of return is compulsory if the taxable income exceeds the basic exemption limit even  if the tax payable is nil or refundable.

Yes, you can file the returns of past  years with penalty and interest on tax payable for each year till the date of filing. Attach a detailed covering note explaining the reasons and request to condone the delay. However irrespective of this  penalty and interest on tax payable.

Sir.. for how long back can I file my IT returns... iam okay to pay penalty too if it arises

You will have to pay penalty if you have not filed returns before  march 31st of next financial year. Since your case is that you will have to file past years also I think Rs.5,000/- for one year. However please consult

Aaykar sampark kendra and complete the filing work.

Can I file together for the last 4 years... or will I be having to face legal actions for non-filing. I am ready to file now with penalties. Please advice.

You can file all the past years returns now and attach challans (separately) for tax as well as penalty.

If you file voluntarily now  you need not face any legal action from department.

File it asap, before u get the notice. You can file the returns with interest and call for condonation of penalty citing genuine reasons for non-filing.